Composite materials, particularly carbon fiber-reinforced polymers (CFRP) and glass fiber-reinforced polymers (GFRP), are increasingly used in hydrogen storage and transportation systems due to their high strength-to-weight ratios and corrosion resistance. However, prolonged exposure to hydrogen environments presents unique challenges, including delamination, altered fiber-matrix interactions, and degradation under cyclic loading. These issues are critical in applications such as aerospace and automotive hydrogen storage tanks, where material failure could have severe consequences.

Delamination is a primary concern for composites in hydrogen service. High-pressure hydrogen can permeate the polymer matrix, leading to interfacial debonding between fibers and the matrix. This phenomenon is exacerbated by the small molecular size of hydrogen, which allows it to diffuse into microcracks and voids. Over time, accumulated hydrogen at the fiber-matrix interface weakens adhesion, reducing the composite's structural integrity. Studies on Type IV hydrogen tanks, which use a polymer liner wrapped with CFRP, have shown that delamination can initiate at pressures as low as 35 MPa after repeated filling cycles. The problem is more pronounced in GFRP due to the lower interfacial strength between glass fibers and epoxy matrices compared to carbon fibers.

Fiber-matrix interactions are also significantly affected by hydrogen exposure. Hydrogen molecules can react with the polymer matrix, causing plasticization or chemical degradation. In CFRP, hydrogen-induced swelling of the epoxy matrix can lead to microcracking, which further accelerates hydrogen ingress. Research on automotive hydrogen tanks has demonstrated that cyclic exposure to hydrogen at 70 MPa can reduce the interlaminar shear strength of CFRP by up to 15% after 1,000 cycles. GFRP exhibits similar but less severe degradation due to the inherently higher ductility of glass fibers, which can accommodate some matrix swelling without catastrophic failure.

Cyclic loading effects are another critical factor, particularly in applications where tanks undergo frequent pressurization and depressurization. Composite materials experience fatigue crack growth under cyclic hydrogen exposure, with cracks propagating preferentially along fiber-matrix interfaces. Aerospace case studies involving cryogenic hydrogen storage have shown that CFRP liners subjected to thermal and pressure cycling develop microcracks that coalesce into larger delaminations over time. In one study, a CFRP tank designed for 15,000 cycles failed prematurely at 10,000 cycles when exposed to hydrogen at -253°C, highlighting the combined effects of low temperature and gas permeation.

Automotive applications provide additional insights into the long-term behavior of composites under hydrogen exposure. Type IV tanks used in fuel cell vehicles are typically designed for a 15-year service life with regular refueling cycles. Accelerated aging tests simulating 10,000 refueling cycles at 70 MPa have revealed that CFRP retains approximately 80% of its initial burst pressure, while GFRP retains around 85%. The difference is attributed to the greater susceptibility of carbon fibers to hydrogen embrittlement compared to glass fibers. However, CFRP remains the preferred material for high-performance applications due to its superior mechanical properties.

Mitigation strategies are being developed to address these challenges. Surface treatments of fibers, such as plasma or chemical functionalization, can enhance interfacial adhesion and reduce hydrogen permeation. Novel matrix materials with lower hydrogen solubility are also under investigation. In aerospace, hybrid composites combining CFRP with thin metal layers have shown promise in reducing hydrogen diffusion while maintaining weight savings.

In summary, composite materials like CFRP and GFRP exhibit complex behaviors under hydrogen exposure, with delamination, fiber-matrix degradation, and cyclic loading effects posing significant challenges. Case studies from aerospace and automotive hydrogen storage systems underscore the need for advanced material solutions to ensure long-term reliability. Ongoing research focuses on improving interfacial properties and developing hydrogen-resistant matrices to extend the service life of composite-based hydrogen infrastructure.